In vitro models of B lymphocyte development.

B lymphocyte differentiation proceeds in the bone marrow in association with a supporting framework of stromal cells. The various long-term bone marrow cultures have provided valuable in vitro models for the study of both normal and dysregulated, stromal cell dependent B lymphopoiesis. Stromal cell lines have been cloned from the adherent layers of the cultures, and recent studies indicate these cells produce soluble factors that control the growth and differentiation of B lineage cells. Modifications of the long-term cultures are now being developed that permit specific stages in the B cell developmental pathway to be amplified. These systems should prove valuable for analysis of stromal cell derived signals that regulate the growth and differentiation of B lineage cells.